Effects of temperature and pressure on wax precipitation and melting characteristics of oil-gas condensate: an experimental and simulation study

The BZ and DB blocks in Tarim Oilfield (China) are condensate gas reservoirs operating under high pressure and high temperature. To mitigate and control the problem of wax deposition, in this study, the wax appearance temperature (WAT) at different cooling rates and wax melting temperature (WMT) at different heating rates of the condensate oil were tested using differential scanning calorimetry. In addition, the crystalline behaviors of wax during precipitation and melting were observed from a micro perspective. By considering the components of the condensate gas and the production data, the carbon number distribution of the well fluids under stratigraphic conditions was simulated. Based on the results, the phase envelope of the well fluids was also simulated, and the relationships between the phase and the temperature and pressure of the oil-gas condensate were analyzed. The temperature and pressure at different depths of the wells were simulated. It was found that the WAT decreased with increasing cooling rate and the WMT increased with increasing heating rate. Furthermore, the wax content of the oil-gas condensate in DB was higher than that in BZ. Finally, it was predicted that wax precipitation occurred above the depth of 500 m in the BZ well.